The present invention is related to a helical antenna, which is provided on a portable radiotelephone, such as a cellular telephone.
Cellular telephones have come into widespread use recently, and antennas are provided on these cellular telephones for the transmitting and receiving of telephone calls and data. As this antenna, a helical antenna, which is mounted in a fixed condition to and protrudes only slightly from the casing of the cellular telephone for convenience of carrying, is well known.
An example of the constitution of a prior helical antenna such as this is shown in FIG. 12.
The helical antenna 100 shown in this figure is constituted from a coil element 113, in which a coil portion 113a is formed; a top cover portion 110, which is integrally molded so as to cover this coil element 113; and a metal base fixture 112, to which the bottom end of coil portion 113a is connected electrically, and, in addition, to which the bottom end of top cover portion 110 is molded.
In the prior helical antenna 100 shown in FIG. 12, coil element 113 comprises an insulative main casing formed in an approximately cylindrical shape, and a helical groove formed in the peripheral surface of the main body. Coil portion 113a is formed inside this groove by either depositing or attaching a metallic thin film thereinto. Helical antenna 100 is made by screwing the bottom end of the coil element 113 formed in this manner onto the top part of metal base fixture 112, and integrally molding top cover portion 110 so as to cover the entire coil element 113 and the top part of metal base fixture 112. Then, helical antenna 100 is mounted in a fixed condition to the casing of a portable radiotelephone by screwing a screw portion 112a formed in the bottom part of metal base fixture 112 into a mounting fixture provided in the casing of the portable radiotelephone.
However, the problem with a prior helical antenna 100 was that the number of processes for making coil element 113 were numerous, and it took time to assemble the helical antenna 100, thus causing costs to rise. Another problem was that because the helical antenna 100 was mounted in a fixed condition to the casing of a portable radio by screwing the helical antenna 100 thereto, special tools were required for mounting, and, in addition, it took time.
Accordingly, an object of the present invention is to provide a helical antenna, which can be assembled easily and can reduce costs, and, in addition, can be readily mounted in a fixed condition.
To solve for the above-mentioned problems, a helical antenna of the present invention comprises a top cover portion, which comprises an approximately cylindrical storing portion, the one end of which is closed, and on which is formed a plurality of coupling members, which extend from the bottom part; a coil portion wound in a coil shape; a coil element comprising a leading portion, which extends from one end of this coil portion; a bobbin, which supports the above-mentioned coil portion of this coil element, and in which a through-hole, through which the above-mentioned leading portion is passed, is formed approximately parallel to the central axis; a holding member, which is mounted to the bottom part of this bobbin, and is positioned on the peripheral surface thereof; and a conductive contact terminal, in which is formed press-fitting members, which are positioned on the inside of the above-mentioned through-hole. The tip of the above-mentioned leading portion, which passes through the inside of the above-mentioned through-hole, is press-fitted inside the above-mentioned press-fitting members of the above-mentioned contact terminal, the above-mentioned top cover portion is fitted by insertion to the above-mentioned bobbin, and the top part of the above-mentioned bobbin, which supports the above-mentioned coil portion, is stored inside the above-mentioned storing portion.
Further, in the above-mentioned helical antenna of the present invention, when the above-mentioned coupling members pass through and mate with the power supply fixture disposed in the casing, the holding member of the above-mentioned contact terminal can be electrically connected to the above-mentioned power supply fixture.
Furthermore, in the above-mentioned helical antenna of the present invention, the above-mentioned contact terminal comprises the above-mentioned holding member, which is formed by being bent into a U-shape, and press-fitting members comprising approximately parallelly positioned elongated plates formed by rising up from approximately the center portion of this holding member, and raised tabs can be formed on these press-fitting members so that [the contact terminal] does not slip out when inserted into the above-mentioned through-hole.
Furthermore, a plurality of ribs is formed on the bottom part of the above-mentioned bobbin, and the above-mentioned coupling members can be arranged between the above-mentioned ribs when the above-mentioned top cover portion is inserted into the above-mentioned bobbin.
Furthermore, in the above-mentioned helical antenna of the present invention, when the above-mentioned contact terminal is mounted to the bottom part of the above-mentioned bobbin, the above-mentioned holding member can be positioned inside the grooved portions formed on the surface of the above-mentioned ribs.
Furthermore, in the above-mentioned helical antenna of the present invention, the cross-sectional shape of the through-hole formed in the bottom part of the above-mentioned bobbin, into which the above-mentioned press-fitting members are inserted, represents an H shape, and the cross-sectional shape of the through-hole, through which the above-mentioned leading portion is passed in the above-mentioned coil element, represents an I shape, and the bottom end of the above-mentioned leading portion can be folded.
According to this present invention, the tip of the leading portion of the coil element, which passes through the inside of the bobbin through-hole, is press-fitted inside the press-fitting members of the contact terminal arranged inside the through-hole, and the top part of the bobbin, which supports the coil portion, is stored inside the storing portion by the top cover portion being fitted in the bobbin by being inserted therein. Thus, assembly of a helical antenna can be performed easily without using special tools, making it possible to reduce costs.
Further, by inserting the helical antenna into a power supply fixture disposed in the casing of a portable radiotelephone, coupling members disposed on the top cover portion mate with the power supply fixture, making it possible for the helical antenna to be mounted to the casing [of a portable radiotelephone] in a fixed condition. This enables the helical antenna to be mounted in a fixed condition to the casing [of a portable radiotelephone] easily and in a short period of time.
Furthermore, since the contact terminal can be formed by processing sheet metal, the coil element can be formed by processing a wire into a coil shape, and the bobbin and top cover portion can be readily formed by plastic molding, each part can be made easily, enabling the cost of the helical antenna to be reduced.